In the modern world, communications are passed between parties in a variety of different ways utilizing many different communications media. Electronic communication is becoming increasingly popular as an efficient manner of transferring information, and electronic mail in particular is proliferating due to the immediacy of the medium.
Unfortunately, drawbacks accompany the benefits provided by electronic communication, particularly in the area of privacy. Electronic communications may be intercepted by unintended recipients. Wireless transmissions, such as voice communication by cellular telephone, and electronic mail are especially susceptible to such interception.
The problem of electronic communication privacy has been addressed, and solutions to the problem have been put in place. One form of solution uses cryptography to provide privacy for electronic communication. Cryptography involves the encrypting or encoding of a transmitted or stored message, followed by the decryption or decoding of a received or retrieved message. The message usually takes the form of a digital signal, or a digitized analog signal. If the communication is intercepted during transmission or is extracted from storage by an unauthorized entity, the message is worthless to the interloper, who does not possess the means to decrypt the encrypted message.
In a system utilizing cryptography, the encrypting side of the communication incorporates an encoding device or encrypting engine. The encoding device accepts the plaintext (unencrypted) message and a cryptographic key, and encrypts the plaintext message with the key according to an encrypt relation that is predetermined for the plaintext communication and the key. That is, the message is manipulated with the key in a predetermined manner set forth by the text/key relation to produce a ciphertext (encrypted) message.
Likewise, the decrypting side of the communication incorporates a decoding device or decrypting engine. The decoding device accepts the ciphertext message and a cryptographic key, and decrypts the ciphertext message with the key according to a decrypt relation that is predetermined for the ciphertext message and the key. That is, the message is manipulated with the key in a predetermined manner set forth by the text/key relation to produce a new plaintext message that corresponds with the original plaintext message.
The manner in which the key and the relation are applied in the communication process, and the manner in which keys are managed, define a cryptographic scheme. There are many conventional cryptographic schemes in use today. For example, probably the most popular of these is a public-key cryptographic scheme. According to a scheme of this type, the keys used are actually combinations of a public key component that is available to anyone or to a large group of entities, and a private key component that is specific to the particular communication.
An important consideration in determining whether a particular cryptographic scheme is adequate for the application is the degree of difficulty necessary to defeat the cryptography, that is, the amount of effort required for an unauthorized person to decrypt the encrypted message. One way to improve the security of the cryptographic scheme is to minimize the likelihood that a valid key can be stolen, calculated, or discovered. The more difficult it is for an unauthorized person to obtain a valid key, the more secure communications will be under a particular scheme.